Comparison of Two Different Methods for Tigecycline Susceptibility Testing in Acinetobacter Baumannii

Abstract

SUMMARY – Tigecycline susceptibility testing (TST) presents a tremendous challenge for clinical microbiologists. Previous studies have shown that the Epsilometer test (E-test) and Vitek 2 automated system significantly overestimate the minimum inhibitory concentrations for tigecycline resistance compared to the broth microdilution method (BMM). This leads to very major errors or false susceptibility (i.e. the isolate is called susceptible when it is actually resistant). The aim of this study was to compare E-test against BMM for TST in carbapenem-resistant and carbapenem-susceptible Acinetobacter (A.) baumannii and to analyze changes in tigecycline susceptibility between two time periods (2009-2012 and 2013-2014), with BMM as the gold standard. Using the EUCAST criteria, the rate of resistance to tigecycline for the OXA-23 MBL-positive, OXA-23 MBL-negative and carbapenemase-negative strains for BMM was 54.5% (6/11), 29.4% (5/17) and 2.7% (1/37), respectively; the OXA-24/40 and OXA-58 producing organisms did not exhibit any resistance. With E-test, all OXA-23 MBL-positive organisms (11/11), 23.5% (4/17) of OXA-23 MBL-negative, and 4.1% of OXA-24/40 (3/74) strains displayed tigecycline resistance; there were no resistant strains among the OXA-58 and carbapenemase-negative isolates. Resistance emerged in the bacterial isolates from 2013 to 2014. Although tigecycline does not display cross-resistance, the highest rates of resistant A. baumannii isolates were observed among those producing VIM MBL, regardless of the testing method. These findings suggest that the commercial E-test does not provide reliable results for TST of A. baumannii . Further confirmation with the dilution method should be recommended, particularly in cases of serious infections.

Investigation of Tigecycline Susceptibility of Multidrug-Resistant Acinetobacter Baumannii Isolates by Disc Diffusion, Agar Gradient and Broth Microdilution Tests

“…Bedenic et al . have reported that AGT (E-test) did not provide reliable results ( 14 ). Interestingly, Akın et al .…”

Calycosin enhances the bactericidal efficacy of polymyxin B by inhibiting MCR‐1 in vitro

“…The data were rendered as the mean AE standard deviation. resistant Gram-negative bacteria or carbapenemase-producing bacteria (Bedenic et al 2018). MCR-1 has attracted widespread global attention because it is a plasmid-mediated resistance gene that can cause bacterial resistance to polymyxins.…”

“…This has gradually led to some antibiotics becoming unsuccessful in clinical treatment and limits the choice of treatment options. Because of resistance to common antibiotics, polymyxin B and colistin (polymyxin E) are used as the last‐resort antibiotics to treat infections associated with multidrug‐resistant Gram‐negative bacteria or carbapenemase‐producing bacteria (Bedenic et al 2018). MCR‐1 has attracted widespread global attention because it is a plasmid‐mediated resistance gene that can cause bacterial resistance to polymyxins.…”

Thymol-Decorated Gold Nanoparticles for Curing Clinical Infections Caused by Bacteria Resistant to Last-Resort Antibiotics

“…Antibiotics such as tigecycline (TGC) and colistin (COL) are used as a last resort for the treatment of diseases caused by MDR bacteria. Since their recent reinstallation in clinical practice, TGC- and COL-resistant microbial isolates have already been reported ( 4 , 5 ). Ceftazidime-avibactam (CZA), a cephalosporin–β-lactamase inhibitor combination with a broad antibacterial spectrum, was introduced in 2015 and is regarded as a last-resort antibiotic ( 6 ).…”